I. Field of the Invention
This invention pertains to a method for making terminal welds in lead storage batteries and to products produced by that method.
II. Description of the Prior Art
Lead storage batteries are often made with straps connecting the individual plates in a stack together. The strap has a vertical portion called a lug. Terminals are provided in the battery for connection of the battery to external electrical cables, the terminals in some batteries being positioned in the battery side walls. A portion of the surface of the lug overlaps a portion of the inside surface of the terminal and the two must be connected together to form a good electrical connection. In one approach, the overlapping surfaces of the lug and terminal are pressed together by welding jaws and electrically-welded connection is formed. One problem with this approach is that the overlapping area of contact creates a low electrical resistance resulting in insufficient heat at the interface causing a cold weld.
Alternatively, it is known to provide the lug portion with a projection which is inserted through a hole in a battery wall and into a hole or cavity on the terminal. A complete connection between the terminal and the lug and a good seal between the terminal, battery wall and lug is obtained by exerting pressure on either side of the connection, that is, by applying pressure against the battery lug within the battery and against the terminal outside the battery so as to squeeze them together and seal the connection against the battery wall. If desired, the step of fusing the connection together can be added by applying heat to the lug and to the terminal. See U.S. Pat. Nos. 3,457,118 and 3,303,056.
A similar approach to making electrical connections through storage battery partitions or walls within the battery case is disclosed in U.S. Pat. Nos. 3,798,071; 3,723,699; 3,687,734; 3,589,948; 3,388,005; and 3,313,658. In particular, the Allen U.S. Pat. No. 3,723,699 discloses a method of making an intercell connection by providing a lug on one side of a partition with a bar thereon which extends into a hole in the partition wall. The lug on the other side of the partition does not have a bar but has a flat surface adjacent the partition. A specially shaped electrode acts on the smooth lug, which has no bar, forcing the soft lead of the lug to press into the hole in the partition wall against the bar on the opposite lug. Then, while under pressure, a current is passed fusing the two lugs together.
Problems can occur in obtaining precise alignment between the relatively large protrusion and openings on various parts to be connected together or between the protrusions and openings in a partition wall or a battery case wall through which the protrusions must pass. In addition, the area of contact between the protrusions on one part of the surface or opening on the other part is relatively large and requires a great deal of heat in order to melt the lead and fuse the parts together to form the terminal connection.